Exploring Poncirus trifoliata Fruits as a Source of Natural Antioxidants: Influence of Ripening Stage

Introduction

Poncirus trifoliata (L.) Raf. (Rutaceae), known as trifoliate orange, is a deciduous species characterized by small yellow-orange fruits, closely related to Citrus species. The fruits are traditionally employed in the preparation of jams, beverages and as herbal remedies in some Asian countries. Recently, P. trifoliata has attracted scientific interest because of its phytochemical profile including phenolic acids, flavonoids, coumarins, limonoids and essential oils. These phytochemicals have been associated with several biological activities, such as antioxidant, anti-inflammatory, antimicrobial and anticancer effects. The novelty of this study is the comparative investigation of immature and mature P. trifoliata fruits, providing new insights into the influence of fruit maturity on phytochemical composition and bioactive properties while supporting their sustainable reuse as agro-industrial by-products.

Methods

The peel of immature and mature fruits of P. trifoliata has been exhaustively extracted by maceration using ethanol as solvent. The antioxidant activity was assessed by applying different in vitro tests including DPPH, ABTS, FRAP and b-carotene bleaching assays and results were analysed in relation to the total phenol content (TPC) and total flavonoid content (TFC).

Results and Discussion

The total phenolic and flavonoid contents were found to be slightly higher in mature fruits (106.7 mg chlorogenic acid equivalents/g and 37.3 mg quercetin equivalents/g, respectively) compared to immature fruits (100.3 mg/g and 33.0 mg/g). The results showed that both immature peel (FA) and mature peel (FM) extracts of P. trifoliata possess significant antioxidant potential. The FM extract exhibited stronger activity in the DPPH and b-carotene bleaching tests. Conversely, the FA extract showed higher efficacy in the ABTS test and a greater FRAP value (17.20 μM Fe(II)/g) compared to the FM extract (10.90 μM Fe(II)/g).

Conclusions

These preliminary findings highlight the potential of P. trifoliata fruit by-product as a valuable source of natural antioxidants.